1. Field of the Invention
This invention relates to electron microscopy and more particularly to equipment for preparing specimens for viewing in an electron microscope.
2. Description of the Prior Art
Before a specimen may be viewed in an electron microscope, it must be processed to remove any water therein and to embed it in a suitable holding medium. Conventionally, the water is removed from a sample of tissue or other material by immersing the specimen in a series of solvent solutions. Each solution contains successively less water than the preceding solution until the final solution is reached, which is water-free. Alternatively, the water in a specimen may be removed by freeze-drying, as described in Grasenick et. al., U.S. Pat. No. 3,536,911. Conventionally, the dehydrated specimen is then placed in a liquid medium capable of polymerization, whereupon the medium is subjected to heat or treated with a catalyst so as to cause it to polymerize into a solid plastic block.
To complete the preparation of the specimen for viewing, it is then necessary to trim the plastic embedding medium to the desired shape and size, to select and isolate that portion of the specimen which the viewer desires to study, and to polish the surface of the plastic to a high degree of smoothness, as is discussed in Szebenyi, et al., U.S. Pat. No. 3,806,577.
These conventional procedures, and other generally related procedures for embedding objects in plastic or other media are described in Magnus, U.S. Pat. No. 2,747,230; McCormick, U.S. Pat. No. 2,996,762; Homeburger, U.S. Pat. No. 3,130,099; Grasenick, et al., U.S. Pat. No. 3,536,911; Halpert, U.S. Pat. No. 3,558,776; and Szebenyi, et al., U.S. Pat. No. 3,806,577.
Specimens for microscopy conventionally are cut into very thin slices by the use of a microtome or similar instrument. These slices are small and fragile, making difficult any attempt to excise a small portion of a slice and embed it in a plastic block in such a manner that the slice remains flat and with a known orientation within the block. The prior art does not disclose convenient means for selecting and isolating a small portion of a specimen prior to embedding or for controlling its configuration and orientation during the embedding process.